This invention relates to an apparatus for classifying particles comprising a main body having a fine particle outlet and a coarse particle outlet, a classifying fan wheel rotatably disposed within the main body and having an inside space in communication with the fine particle outlet, and a first gas inlet channel communicating with the interior of the main body for supplying the particles to be classified (hereinafter referred to simply as "particles") to the fan wheel externally thereof along with a gas flow.
With classifying apparatus of this type, the particles supplied thereto as entrained in a flow of gas are given a centrifugal force by a classifying fan wheel rotating within the main body of the apparatus, while the gas is adapted to pass through the fan wheel and flow out from the apparatus. The difference between the centrifugal force and the centripetal force simultaneously given to the particles in the gas flow acts to selectively separate the particles. For this operation, it is desired that the particles be thoroughly dispersed through the gas flow, but conventional apparatus are unable to effect full dispersion, with the result that some fine particles among the particles are likely to remain agglomerated without separating into individual particles and flow into a coarse particle zone to mingle with coarse particles. This leads to reduced fine or coarse particle collection efficiency and lower classification efficiency.